Heat stress and ACTH administration on cortisol and insulin-like growth factor I (IGF-I) levels in lactating Holstein cows

Figures & data

Figure 1. Daily air temperature, relative humidity and THI during thermal comfort (Treatment 1).

Table 1. Meteorological data monitored 24 h during Treatment 2 and Treatment 3.

Variables	Air temperature (°C)	Relative humidity (%)	THI (index value)
Treatment 2
Mean	16.5	67.2	63
Min–max	10.2–29.4	45–99	52.2–70.3
Treatment 3
Mean	29.3	74.1	80
Min–max	26.0–38.0	71–84	75.5–96.6

Table 2. Least-square means and standard error (SEM) of RT, respiratory frequency (RF), CORT and IGF-I concentration measured in experimental cows under thermal comfort.

Time sampling Data	08:00 h Mean±SEM	13:00 h Mean±SEM
RT (°C)	37.95^a±0.09	38.55^b±0.06
RF (mov/min)	40.42^a±2.28	54.03^b±2.04
Cortisol (ng/ml)	4.97±0.44	4.64±0.39
IGF-I (ng/ml)	64.09±16.12	67.4±11.80

Note: Means within a line labelled with different letters differ (P ≤ .05).

Figure 2. Cortisol and IGF-I levels (ng/ml) before and after ACTH administration in experimental cows. The values are means and standard errors of the mean. Means labelled with different letters differ (P ≤ .05) within time.

Figure 3. Cortisol and IGF-I levels (ng/ml) measured on 18th, 20th and 22nd day of the experimental period in cows submitted to heat stress during seven consecutive days (from 16th to 22nd). The values are means and standard errors of the mean. Means labelled with different letters differ (P ≤ .05) on day within sampling time.

Table 3. Least square means and standard error (SEM) of RT and RF measured in experimental cows under heat stress (T3).

Time sampling Data	07:45 h Mean±SEM	08:00 h Mean±SEM	09:00 h Mean±SEM	10:00 h Mean±SEM	13:00 h Mean±SEM
RT (°C)	38.02^a±0.08	38.10^a±0.14	38.84^b±0.15	39.81^b±0.13	39.83^b±0.12
RF (mov/min)	45.03^a±2.28	44.42^a±2.04	65.01^b±4.22	74.07^b±4.93	66.08^b±3.61

Note: Means within a line labelled with different letters differ (P ≤ .05).

Figure 4. Milk production in five lactating cows before (day 13–15), during (day 16–22) and after (day 23–28) heat stress period. Values are means and standard errors of the mean. Means labelled with different letters differ (P ≤ .05) within day.

Figure 5. Total amount of CORT and IFG-I measured on experimental tests. Total amount based on all samples taken, the value of the integrated AUC corrected for basal levels. Means labelled with different letters differ (P ≤ .05).